1. Field of Endeavor
The disclosure relates to a premix burner for a gas turbine, in particular to a nozzle for atomising liquid fuel in a premix burner with a conical swirl generator and a subsequent cylindrical mixing section.
2. Brief Description of the Related Art
Premix burners with a conical swirl generator and a subsequent cylindrical mixing section are known, for example, from EP918191. The swirl generator, which serves as a premix section, has conical interleaved sections, the longitudinal axes of which are in each case offset with respect to one another. Compressed combustion air passes through tangential inflow passages between the walls of the conical sections into the mixing space of the swirl generator. A fuel is introduced via one or more nozzles or alternatively via fuel lines along the tangential air inflow passages into the mixing space, where it is mixed with the air. Further premixing of air and fuel is achieved in the subsequent mixing section, in that the latter produces high-quality mixing on account of the flows being routed without any losses. The mixing section also performs the function of preventing flashback of the flame from the combustion chamber into which the mixing section expands.
A further premix burner of this type is disclosed in DE 103 55 930. The outlet region of the mixing section is, in that case, provided with undulations which generate axial swirls and as a result influence the turbulence in the outlet region and the flow stability. The fuel is introduced axially via a nozzle into the conical swirl generator, with the nozzle opening lying on the longitudinal axis of the premix burner.
DE 197 30 617 discloses a two-stage pressure atomiser nozzle for use in combustion technology with two coaxial tubes and a mixing chamber into which two feed passages lead. A nozzle outlet bore lies on the axis of the nozzle tubes and has a diameter which is in a given ratio to the diameter of the feed passages.
DE 44 40 558 discloses a premix burner with a conical swirl generator. The fuel is introduced via a nozzle with openings which do not lie on the longitudinal axis of the nozzle. The angle between the resulting spray cones and the longitudinal axis of the nozzle is in particular larger than the divergence angle of the conical part of the swirl generator. The abovementioned fuel nozzle is designed specifically for a premix burner without a cylindrical mixing section.
EP 899 508 discloses a premix burner with a swirl generator having a cylindrically formed mixing section as described in the introduction, and in particular a fuel nozzle with nozzle tubes 104 which each generate a fuel jet with an injection angle with respect to the central axis of the fuel nozzle which is equal to the divergence angle of the cone of the swirl generator.
EP 902233 discloses a combined pressure atomiser nozzle for a gas turbine burner with swirl generator, the nozzle body of which has two separate feed passages, from each of which an outlet opening leads into the mixing space of the burner. The nozzle body therefore has two different nozzles, namely: a radially outer multi-hole nozzle with outlet openings arranged off-center; and a central nozzle, lying on the longitudinal axis, with a centrally arranged outlet opening. The outlet openings arranged off-center are positioned in such a way that the spray cones are directed into the wake of the cone shells of the swirl generator. At full load, this nozzle is operated by way of the outlet openings positioned off-center. At partial load, the nozzle is switched over to the central outlet openings, in order to prevent drops of fuel oil being deposited on the walls of the swirl generator.
DE 19536837 discloses an apparatus for injecting fuels having a swirl chamber within the injection apparatus or nozzle. An axially running air feed passage 5 and a fuel passage 2 which runs parallel to the longitudinal axis of the nozzle lead into this swirl chamber 1, in which air and fuel in a first phase are mixed while they are still inside the nozzle. As seen in the direction of flow, the swirl chamber has a conically narrowed section, through which the air/fuel mix flows, ultimately passing via an outlet opening lying on the longitudinal axis of the nozzle into a burner mixing space. The only outlet opening from the nozzle is arranged on the longitudinal axis of the nozzle.